The invention relates to the selective hydrogenation of diolefins contained in a monoolefin-containing hydrocarbon stream and to the removal of arsenic therefrom. The invention also relates to a catalyst composition that is useful in the removal of arsenic and in the selective hydrogenation of diolefins contained in a monoolefin-containing hydrocarbon stream, and it relates to a method of making such a catalyst.
Gasoline regulations are increasingly creating a need to treat various refinery streams and products, for example, cracked gasoline blending material including coker naphtha and catalytically cracked gasoline, to remove the undesirable sulfur, arsenic and diolefin compounds contained in such refinery streams and products.
The removal of arsenic or arsenic compounds from a cracked gasoline blending material is of particular concern due to the poisoning effect that arsenic has on the catalysts used in subsequent or downstream treatment steps. It is, thus, desirable to remove the arsenic from a hydrocarbon stream having a concentration of arsenic prior to its further processing with an arsenic sensitive catalyst.
As for the presence of diolefins in a cracked gasoline material, these, too, can be undesirable compounds; since, they can cause a gasoline end product to be unstable, or they can cause unwanted problems in the further downstream processing of the cracked gasoline material.
It is desirable to have a process for catalytically removing both arsenic and diolefins that are contained in a cracked gasoline blending material having a concentration of monoolefins. One difficulty with such a process is finding a catalyst that will be able to remove the arsenic from such a process stream while still maintaining its activity for the hydrogenation of diolefins or sulfur, or both. Moreover, it is especially difficult for such a catalyst to have the dual functionality of the capacity to remove arsenic and to selectively hydrogenate diolefins contained in a cracked gasoline blending material without hydrogenating a significant portion of the monoolefins also contained therein.